1. Field of the Invention
The present invention relates to a resin composition which can be adhered directly to a metal by means of injection molding without the use of any adhesive, can be preferably used as a material for a variety of composite products, and has favorable adhesivity. The present invention relates also to a gasket material which can be adhered directly to a metallic cover body and the like by means of injection molding without the use of any adhesive, and has favorable adhesivity to a cover body and the like.
2. Description of the Related Arts
An elastomer having a low hardness is in a wide range of demand as a gasket material for hard disc units, an ink sealing material and the like, and is advantageous in that when being integrated with a metallic member into a composite product, the characteristics of its own are sufficiently exhibited. In particular, an elastomer having a low hardness is widely used as a gasket material for hard disc units, and is advantageous in that the characteristics of its own are sufficiently exhibited, when it is used in the form of a gasketed cover or a gasket fitted to a frame by integrating with a metallic cover body or a metallic frame body.
In order to integrate an elastomer having a low hardness with a metal, there have heretofore been adopted such methods as {circle around (1)} the use of an adhesive, {circle around (2)} the use of an acid-modified styrenic thermoplastic elastomer as an elastomer having a low hardness, {circle around (3)} physical integration of a metal and an elastomer having a low hardness by the working of the metal, and the like methods.
However, the above-mentioned method {circle around (1)} is involved in the problems that it necessitates a coating step for an adhesive, it requires process control for coating and drying of the adhesive, thus making it troublesome, and besides the adhesive generates impurities such as a volatile matter. Moreover, the above-mentioned method {circle around (2)} is involved in the problems that because of the polymer being modified, the elastomer having a low hardness is deteriorated in various physical properties, especially compression set, and further the modification is accompanied by the generation of such impurities as residual catalyst and unreacted substances. In addition, the above-mentioned method {circle around (3)} is involved in the problems that metal working is troublesome, and it is impossible to carry out integration work of a fine part item, thereby disenabling a metal and the elastomer having a low hardness to be integrated with each other.
Under such circumstances, it is a general object of the present invention to provide a resin composition which can be adhered directly to a metal by means of injection molding without the use of any adhesive, and which is well suited as a material for a variety of composite products.
It is another object of the present invention to provide a gasket material which can be adhered directly to a metal by means of injection molding without the use of any adhesive.
In view of the foregoing, intensive extensive research and investigation were accumulated by the present inventors in order to achieve the above-mentioned objects. As a result, it has been found that the general object can been achieved by using a resin composition (I) wherein a styrenic thermoplastic elastomer composed of a block copolymer is blended with a specific ethylene/(meth)acrylic acid copolymer or an ethylene/(meth) acrylic ester copolymer and a paraffin base oil each in a specific amount.
In addition, it has been found that the another object can been achieved by using a gasket material (I) wherein a styrenic thermoplastic elastomer composed of a block copolymer is blended with a specific ethylene/(meth)acrylic acid copolymer or an ethylene/(meth) acrylic ester copolymer and a paraffin base oil each in a specific amount.
Further, it has been found that the general object can also been achieved by using a resin composition (II) wherein a styrenic thermoplastic elastomer composed of a block copolymer is blended with a maleic anhydride-grafted polyolefin and a paraffin base oil each in a specific amount.
Furthermore, it has been found that the another object can also been achieved by using a gasket material (II) wherein a styrenic thermoplastic elastomer composed of a block copolymer is blended with a maleic anhydride-grafted polyolefin and a paraffin base oil each in a specific amount.
It being so, the present invention has been accomplished on the basis of the above-mentioned findings and information.
Specifically, the present invention provides a resin composition (I) which comprises 100 parts by weight of (a1) a styrenic thermoplastic elastomer composed of a block copolymer; 3 to 50 parts by weight of (b1) an ethylene/(meth)-acrylic acid copolymer or an ethylene/(meth)acrylic ester copolymer each having 5 to 45% by weight of (meth)-acrylic acid content; and 50 to 170 parts by weight of (c1) a paraffin base oil.
In addition, the present invention provides a gasket material (I) which comprises 100 parts by weight of (a1) a styrenic thermoplastic elastomer composed of a block copolymer; 3 to 50 parts by weight of (b1) an ethylene/(meth)-acrylic acid copolymer or an ethylene/(meth)acrylic ester copolymer each having 5 to 45% by weight of (meth)acrylic acid content; and 50 to 170 parts by weight of (c1) a paraffin base oil.
Moreover, the present invention provides a gasketed cover in which a gasket is fitted to a cover body, characterized in that the cover body is made of a metal, the gasket is made of the aforesaid gasket material (I), and said cover body and said gasket are integrated with each other.
Further, the present invention provides a resin composition (II) which comprises 100 parts by weight of (a2) a styrenic thermoplastic elastomer composed of a block copolymer; 1 to 15 parts by weight of (b2) a maleic anhydride-grafted polyolefin; and 30 to 170 parts by weight of (c2) a paraffin base oil.
Still further, the present invention provides a gasket material (II) which comprises 100 parts by weight of (a2) a styrenic thermoplastic elastomer composed of a block copolymer; 1 to 15 parts by weight of (b2) a maleic anhydride-grafted polyolefin; and 30 to 170 parts by weight of (c2) a paraffin base oil.
Furthermore, the present invention provides a gasketed cover in which a gasket is fitted to a cover body, characterized in that the cover body is made of a metal, the gasket is made of the aforesaid gasket material (II), and said cover body and said gasket are integrated with each other.